After the nerve agent attack in Salisbury (UK), the authorities searched for the source. How would they do that ? Do they have a detector that ‘sniffs’ for nerve agents ? It was finally found in a perfume bottle.
Some dumpster divers found it, and became ill when they started spraying it on themselves.
In the army we had detector papers that you stuck on things that were supposed to change colour in the presence of this stuff.
Yes. There are electronic kits and devices that filter the air, and will beep or sound an alarm when they detect a chemical. The US Army, for example, uses the JCADS device. It’s a little handheld doodad with lights that indicate what kind of agent you are dealing with (eg blood, blister, nerve, etc). MK VII already mentioned the paper tests, which come in a couple varieties.
There are also analysis devices like hyperspectral imaging, in which different chemicals and surfaces give off different signatures invisible to the human eye. Optical hyperspectral analysis has been developed to detect chemical and biological agents.
I don’t know the exact chain of events in this case. If I wanted to track down the source of a nerve agent attack, my first plan would be to re-trace the patient’s steps and use these devices to search places, people, and objects the patient might have encountered.
I did serve as a conscript in anti CBR unit and we had chemical basic set, then some electronic detection device (aka tricorder) and some primitive lab on ATV. So we had some basic detection capabilities to determine how long we have to live.
As for this case, it is a wee more complicated. That was specific tailored (you got like 100 of more versions) binary agent and you need a lot better equipped and staffed lab to know what are you dealing with.